A Nottingham academic says legislation requiring parents to be notified over abortions for the under 16s could see a drop in teenage pregnancy.
MPs rejected a bid to force doctors offering abortion or contraception advice to under-16s to inform the child's parents on Wednesday.
Professor David Paton said studies in the United States demonstrated a new law could cut teenage pregnancies.
He said research had revealed that STDs amongst teenagers also fell.
Professor Paton, who supported the bid by Tory MP Angela Watkinson, said: "There are different areas of the United States where parents have to be involved in abortion and pretty much all of these studies have shown abortion rates have dropped as we'd expect... and overall we see a drop in teenage pregnancies.
"What seems to be happening is that young people, when they know their parents will have to be involved, they tend to take a little bit more care, perhaps some of them don't have sex in the first place."
Anne Weyman, chief executive of the FPA (formerly the Family Planning Association) has argued that a law of this kind would deter young people from seeking essential advice.
MPs voted by 159 to 87 to retain the current guidelines guaranteeing confidential advice to under-16s.